"He's not an easy guy to face," Arizona manager Chip Hale said.
Indeed, the 13 strikeouts Sunday were the most by a Reds rookie since Gary Nolan fanned 15 on June 7, 1967, against San Francisco.
"I tried to keep the same pattern I had back in Arizona," said Iglesias (3-5, 3.93 ERA), who allowed one run in six innings of a 2-0 Aug. 7 loss against the D-backs.
"I was trying to attack them in the beginning. I was trying to get ahead of the hitters using my slider. My slider was working really well today as well as my changeup.